Temperature compensator for spring scales



Nov. 3, 1925. 1,559,573

G. M. LUDLOW TEMPERATURE COMPENSATOR FOR SPRING SCALES Filed Dec. 5,1921 4 =5 E *5 J72 06/2102 $572655 5 Faye/2 fiadiow,

Patented Nov. 3, 1925.

UNITED STATES 1,559,573 PATENT OFFICE.

GEORGE M. LUDLOW, OF EVANSTON, ILLINOIS, ASSIGNOR T0 SANITARY SCALE COM-PANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

TEMPERATURE COMPENSATOR FOR SPRING SCALES.

Application filed December 3, 1921. Serial No. 519,581.

T 0 all whom, it may concern:

Be it known that I, GEORGE M. LUnLow, a citizen of the United States,residing at Evanston, in the county of Cook and State of Illinois, haveinvented certain new and useful Improvements in Temperature Compensatorsfor Spring Scales, of which the following is a specification.

This invention relates to means for correcting the weighing effect of aspring balanced scale to compensate for changes in atmospherictemperature.

It has heretofore been proposed to thermostatically modify the leveragethrough which a loadiacts upon the spring balanced weighing mechanism ofa scale for the purposeabove stated, and in accomplishing this athermostat has been mounted upon the weighing lever in a manner .totransmit movements resulting from its expansion and contraction,directly to a longitudinally adjustable part of the lever, withtheeffect of shortening the leverage and increasingthe load upon the springwhen the temperature falls and the spring becomes stiffer, andlengthening the leverage ,to decrease the load when the spring becomesmore yielding under a rise in temperature. But such an arrangement,while tending to correct the error of the scale due to change intemperature, involves the disadvantage of shifting the center of gravityof the weighing lever in the direction to aggravate the error witheach'length adjustment rather than correct it, and thus requires anexcessive leverage adjustment besides affecting the absolute initialload of the lever. The present invention has for its object to avoid theabove mentioned disadvantage, and consists in combining a thermostaticdevice with a weighing lever in a manner to cause the thermostaticdevice to move in the same direction as the center of gravity of thelever, so that it assists directly in establishing said center ofgravity, that is to say to ward the lever fulcrum when it is necessaryto decrease the initial load of the lever upon the spring, as the latterbecomes more yielding under a rise in temperature and away from thefulcrum, to increase the initial load of the lever upon the spring, whenthe latter becomes more resistant under a drop in temperature; saidthermostat being caused to develop such movements, directly with changesin the center of gravity, as distinguished from inversely thereto, in asuitable counter-poise which also moves directly with the thermostat andtherefore with changes in center of gravity, which may exist simply inthe structure of the thermostat itself'or in some of its transmittingconnections or be definitely provided in the form of a weight which thethermostat moves.

Inasmuch as changes in leverage are desirable' in temperaturecompensation in scales, in addition to changes in center of gravity, theobject of the present invention is best realized by having thethermostat, operating as aforesaid, also impart move ment to theload-transmitting element at the free end of the lever, and in doing sothe thermostat moves oppositely to the loadtransmitting element; that isto say shifts the center of gravity toward the fulcrum as theload-transmitting element moves to extend the length of the lever orvice versa.

Another object of the invention is to provide' an improved means wherebya thermostat operating in the manner described, and controlling acounter-poise as aforesaid, may impart movements to theload-transmitting element of the lever; and accordingly, another featureof the invention consists in connecting the reversely moving thermostatwith the load-transmitting element, through motion reversingconnections, preferably in the form of a pair of levers fulcrumed on thescale lever, and having each one end connected with the free end of thethermostat and its other end with a transmitting frame which is in turnconnected with the loadtransmitting element of the scale lever.

Still another object is to provide an improved form of counter-poise fora thermostat operating upon the principle herein described; and to thisend another feature of the invention consists in providing acounter-balance which moves directly with the thermostat, with avariably rectifying means partaking of the movements of thecounter-poise; a preferred embodiment of this part of the invention alsoincluding the feature of using the counter-poise as a means forconnecting the thermostat with the direction-reversing levers.

In order that the invention may be fully understood, several embodimentsthereof are illustrated in the accompanying drawings, in which-- Figurel is an elevation partly in section of a simple construction of scale ofa type to which the invention is applicable.

Figure 2is a topplan view of theweighing lever employed in Figure 1.

Figure 3 is a front elevation of the weighing lever and its appurtenant;pants Figure 4: is a section on the line i -4Q of Figure 2.

Figure 5 is a detail view of a shot cup employedz in the embodiment ofFigures 2 and" h a 1- represents the casing, 2 the counterbalf ancin-l'spring, 3athesteelyardlrod, ands the weighing; lever of" a known typeof scale.

Lever; 4ciis fulcrumed. at 5, carries knife? edge supports. 6.for=loa.ding tray 7, and has alongitudinal'ly adjustable tongi'ie-8through which it connects with the steelyard rod; 3. In arrangements ofthis kind, spring. 2 is customarily adjusted sothat under the in itialload normally imposed by the lever e andthepa-rts mounted upon it, a;chart or indicator in the casing 1-: will register:

with. zero-. The changes: in temperature causing expansion andcontraction to some extent in tlieloading lever, but'manifesting itselfto much greater-extent in the-counter balancingzspringi 2, will= throwthe. indicator ofi; the zero mark. To remedy. this. defect it. hasheretoforebeen proposed to mount upon the lever- 4s athermostat ofsuitable construction, with one. end ofsthe thermostat fixedly anchored;upon. a rear portion: of? the i levernandl withitsother-Yen'd-rextending forwardly and directly connected to" thetongue, thereby. moving. thetongueoutward andin: Ward withexpansionand;contnaction1oftl1e thermostat due;- to 7 changes; in temperature,-andchanging: the leverage; otthe; load: imposed. upon, the, spring: in,a manner; to maintain the; indicaton chart at: zerofand; changethe-freadingso fli weight vwhen! an:- artis c1e= is: placed; upon the.tray; But with: such,a11ocation-. o-f 1 theefixedifabntmentz Qftthe;thermostat. 9: with relation; to; the; tongue 8, the; centen of?gravity: ofithelevbni dueto the-extension and; retractionotthetheltmost-at; and ofthe; tongue, nioves-.,outwardly when the;leverage increases, and; inwardly;

thermostat is changed in its relation to the lever that carriesit andthe extension of the lever which it affects. This arrangement consistsin locating the thermostat 9. with its fixed abutment at 10. or otherequivalent position, and with its free end 11 presented rearwardlyandthere connected with reversing means which in turn convert itsmovements as imparted? to" the tongue 8, so that while the tongue stillmoves outward under an expansion of the thermostat and inward. under acontraction of thesame, thethemnostat: and some- 0f: its connectedpartsfare: moving in a direction oppositeto that: in, which the tonguemoves and the center of: gravity ofithe: weighing lever tmay beinadesubstantiallyconstant position. The reg versing connection which 13prefer; toiemploy consistslof a. pair of-levers l2reach. provided witha; fixed fulcrum13- upon a; rearportion of: the lever 4', with: one,end; of; each recversing lever connected. through the block:

1 L: with the: free; end ofthe thermostat 9 and with the other ends of:said levers: 0011: nected, respectively, to the; two arms-15' whichextendfirsta laterally: as, at 16.2 and thenrear-wardly, fromthetongue8., Q011 necting block 14 may be made: as; muclIL of a factor asdesiredin deterininingthe;cenv ter of gravity. of: the, lever. t: It; will;pref;- erably be constructed. with a; rectifien. 22b constructed with acup-.22 (Figure: 5 5 to-,re-j ceive shot, in accurately. determining;-he initial-loadaof;thelever; 1 i,

For convenience in mounting the; t-her no stat 9;: and, reversing levers12,; therear end-j of: the Weighing: lever 4i.- is; developedinto theform of a frame; 01; box -like structure with the i, forward; side 17-serving; as the, abutment for, the thermostat w nd thi eat side 18-servingtomount tilt), levers 12,-; The; cross: section. of; the severalparts of; the .lever'e will;prefer lyv ee haamelledr order-rteaecommodateztheg ong efli andi ts extensi ns; 1.5;, .6:, Wi hin; heprevidei g e h ref re: nd v hez eazn an 18 of the leverwilLhe maderemovable; for: convenien e in assembling eipa i s- I T forw rd: endotlhe ongn fi iniaya f desired; b u t in d n he downw r ht presented;-channelof theifronta ndi fi ev r hy means; of a pin 19 extendingthroughtongne- =8-; and, a slot2O in thescalelever.

I: claim: 7

1. In combination with a weighing lever having an adjustable partmovingdongitudie nally thereof for; changing; its leverage, athermostat carried by said lever and; expanding andcontracting thereonin; directions longitudinal of the lever, a- Connection be ween; s idhermost t n aid, part hro g h h: aohlm ement. f) h hat: m stat ismnarted to e i diL-ntablepart in:- reverse direction, and; acounterbalance weight moved byv theexpansion ands con,

traction of the thermostat, in the same directions therewith.

2. In combination with a scale lever 21 load transmitting memberconstructed for extension and retraction in the direction of its length,a thermostat carried by said lever and expanding and contractinglongitudinally thereof under changes in temperature, in directionsopposite to those required in the load-transmitting member, meansreceiving and reversing the movements imparted by said thermostat andtransmitting them in reverse directions to the load transmitting memberand a counter-balance weight moved directly by and in the same directionas the thermostat.

3. In combination with a weighing lever a load transmitting memberconstructed for longitudinal adjustment thereon, a thermostat carried byand fixed at one end upon a forward portion of said lever and with itsother end presented toward the rear end of said lever free to movelongitudinally thereof and carrying a counter-weight, and a reversinglever connecting the free end of said thermostat with said member andimparting longitudinal adjustment thereto opposite to those of thethermostat.

4. In combination with a scale lever having a load transmitting memberconstructed for longitudinal adjustment thereon, a thermostat fixed atone end upon said lever and having its other end free to movelongitudinally thereof, a pair of reversing levers fulcrumed on saidscale lever having each an end connected with the free end of thethermostat, and a transmitting frame connected with the other end ofeach reversing lever and imparting adjustments to the load transmittingmember.

5. In combination with a weighing scale lever, a connecting tonguemounted with freedom of longitudinal movement thereon, and havingrearwardly extending spaced arms, a thermostat having one end fixedlyanchored to the scale lever and its other end presented rearwardlybetween said spaced arms with freedom of movement longltudinally of thescale lever under changes in temperature, and reversing levers fulcrumedupon a rear portion of the scale lever and each having one end connectedwith the free end of the thermostat and its other end connected with anarm of the tongue.

6. In a weighing lever, a load transmitting member adjustable thereonfor influencing the length of said lever, a counterbalance member on thelever having adjustments opposite to those of the load transmittingmember, and a variable rectifying means mounted upon the lever andpartaking of adjusting movements of one of said members.

7. In combination with a weighing lever, a load transmitting memberadjustable thereon, a counterpoise adjustable longitudinally of saidlever oppositely to the movements of said member, a thermostat adaptedto control the positions of said member and said counterpoise, and arectifier mounted on said counterpoise.

Signed at Evanston, Illinois, this 1st day of December, 1921.

GEORGE M. LUDLOW.

